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Abstract:

Concerned with a cylindrical conductive belt for electrophotography which
has made permanent curl less occur. The conductive belt has a continuous
phase containing a thermoplastic polyester resin and discontinuous phases
each containing any one or both selected from a polyether-ester amide and
a polyether amide, and the discontinuous phases are present in such way
as to extend in the peripheral direction of the belt; the belt having a
crystallinity that is lower on the outer-peripheral surface side than on
the inner-peripheral surface side.

Claims:

1. A cylindrical conductive belt for electrophotography comprising: a
continuous phase which comprises a thermoplastic polyester resin; and
discontinuous phases each of which comprises any one or both selected
from a polyether-ester amide and a polyether amide; said discontinuous
phases being present in such way as to extend in the peripheral direction
of said cylindrical conductive belt; wherein a crystallinity of an
outer-peripheral surface side of said cylindrical conductive belt is
lower than that of an inner-peripheral surface side of said cylindrical
conductive belt.

2. The conductive belt according to claim 1, wherein the thermoplastic
polyester resin contains any one or both selected from a polyalkylene
terephthalate and a polyalkylene naphthalate.

3. The conductive belt according to claim 2, wherein the polyalkylene
terephthalate and the polyalkylene naphthalate are polyethylene
terephthalate and polyethylene naphthalate, respectively.

4. An electrophotographic apparatus comprising the conductive belt
according to claim 1 as an intermediate transfer belt.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of International Application No.
PCT/JP2011/000890, filed Feb. 17, 2011, which claims the benefit of
Japanese Patent Application No. 2010-042730, filed Feb. 26, 2010.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a cylindrical conductive belt for
electrophotography, used for intermediate transfer belts or the like of
electrophotographic apparatus, and also relates to an electrophotographic
apparatus.

[0004] 2. Description of the Related Art

[0005] Japanese Patent Application Laid-open No. 2008-89961 discloses a
conductive endless belt used for an intermediate transfer belt of an
electrophotographic image forming apparatus in which belt a
polyether-ester amide is added as a high-molecular ion-conducting agent
to a polyester type elastomer and/or a thermoplastic polyester resin.
When compared with a case of making conductive by using as a conducting
agent an electron-conductive conducting agent such as carbon black, such
a belt may gently change in conductivity against the amount of the
conducting agent to be added, and its electrical resistance can be
controlled with ease.

[0006] Here, the polyester type elastomer or thermoplastic polyester resin
and the polyether-ester amide or polyether amide are fundamentally
incompatible with each other. Hence, the conductive endless belt
disclosed in Japanese Patent Application Laid-open No. 2008-89961 takes a
structure having a continuous phase constituted of a polyester type
thermoplastic elastomer and discontinuous phases each constituted of a
polyether-ester amide copolymer. This accords with what is disclosed in
Japanese Patent Application Laid-open No. 2008-274286 and Japanese Patent
Application Laid-open No. 2005-164674.

SUMMARY OF THE INVENTION

[0007] The present inventors have gone through studies on a cylindrical
conductive belt which has a continuous phase containing a crystalline
thermoplastic polyester resin and discontinuous phases each containing a
polyether-ester amide or polyether amide serving as a conducting agent
and in which the discontinuous phases are present in such way as to
extend in the peripheral direction of the belt.

[0008] Here, the cylindrical conductive belt for electrophotography
commonly has a problem as stated below. That is, the cylindrical
conductive belt for electrophotography is placed in an
electrophotographic apparatus in such a state that it is stretched over a
plurality of rollers at a constant tension. Hence, where the conductive
belt stands continuously at rest over a long period of time, it has come
about that a curl not easily revertible to normal (hereinafter called
"permanent curl") occurs at the part where the belt comes into contact
with any roller to have the largest curvature. Such a portion of the belt
for electrophotography at which the permanent curl has occurred is kept
deformed because of that permanent curl even when that portion has moved
to a position apart from the roller. Hence, toner images may
insufficiently be transferred to such a deformed portion from an
electrophotographic member to cause lines or the like in
electrophotographic images.

[0009] The present inventors have made studies on the mechanism by which
the permanent curl occurs on the above cylindrical conductive belt which
has a continuous phase containing a crystalline thermoplastic polyester
resin and discontinuous phases each containing a polyether-ester amide
and in which the discontinuous phases are present in such way as to
extend in the peripheral direction of the belt. As the result, they have
newly found that the permanent curl occurring in this conductive belt is
particularly caused by such make-up itself.

[0010] Accordingly, the present invention is directed to providing a
cylindrical conductive belt for electrophotography which is made up as
described above, also has superior mechanical strength, and can not
easily cause the permanent curl. Further, the present invention is
directed to providing an electrophotographic apparatus that can stably
form high-grade electrophotographic images.

[0011] According to one aspect of the present invention, there is provided
a cylindrical conductive belt for electrophotography comprising a
continuous phase which comprises a thermoplastic polyester resin, and
discontinuous phases each of which comprises any one or both selected
from a polyether-ester amide and a polyether amide, and the discontinuous
phases are present in such way as to extend in the peripheral direction
of the belt; wherein a crystallinity of an outer-peripheral surface side
of said cylindrical conductive belt is lower than that of an
inner-peripheral surface side of said cylindrical conductive belt.

[0012] According to another aspect of the present invention, there is
provided an electrophotographic apparatus comprising the above conductive
belt as an intermediate transfer belt.

[0013] According to the present invention, a cylindrical conductive belt
for electrophotography can be obtained which can not easily cause the
permanent curl and has superior mechanical strength. According to the
present invention, an electrophotographic apparatus can also be obtained
which can stably form high-grade electrophotographic images.

[0014] Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference to the
attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1A is an illustration of the conductive belt according to the
present invention.

[0016] FIG. 1B is an illustration of the conductive belt according to the
present invention.

[0017]FIG. 2 is an illustration of the mechanism by which the permanent
curl occurs.

[0018]FIG. 3 is an illustration of the electrophotographic apparatus
according to the present invention.

[0019]FIG. 4 is a schematic view of a stretch blow molding machine used
in producing the conductive belt according to the present invention.

DESCRIPTION OF THE EMBODIMENTS

[0020] Preferred embodiments of the present invention will now be
described in detail in accordance with the accompanying drawings.

[0021] The present inventors have analyzed as stated below the mechanism
by which the permanent curl occurs on the cylindrical conductive belt
which has a continuous phase containing a crystalline thermoplastic
polyester resin and discontinuous phases each containing a
polyether-ester amide and in which the discontinuous phases are present
in such way as to extend in the peripheral direction of the belt.

[0022] First, they have grasped that the permanent curl is a state in
which the conductive belt has lost the force of being restored to an
original shape like that of rubber, at its part where it stands wound
around any roller over which it is stretched, and its shape of being kept
wound around the roller is somewhat maintained.

[0023] Here, FIG. 1A is a perspective view of a cylindrical conductive
belt which has a continuous phase containing a thermoplastic polyester
resin and discontinuous phases each containing any one or both selected
from a polyether-ester amide and a polyether amide and in which the
discontinuous phases are present in such way as to extend in the
peripheral direction of the belt. FIG. 1B is a partial enlarged view of a
cross section in the peripheral direction of the belt shown in FIG. 1A.
In FIGS. 1A and 1B, reference numeral 101 denotes the continuous phase
containing a thermoplastic polyester resin (hereinafter also simply
"PE"); and 103, the discontinuous phases each containing any one or both
selected from a polyether-ester amide and a polyether amide. Then, the
discontinuous phases 103 are present in such way as to extend in the
peripheral direction of the conductive belt.

[0024] The present inventors have made observation on a cross section in
the peripheral direction of the belt at the part where the permanent curl
has occurred because the conductive belt having the afore-mentioned
construction, has been stretched over two rolls and left to stand in a
stationary state over a long period of time. As the result, as shown in
FIG. 2, there have been found to be micro-crevices 102 at the interfaces
between a continuous phase and discontinuous phases present on the
outer-peripheral surface side of the conductive belt. These
micro-crevices are considered to have been caused by the difference in
behavior between the continuous phase and the discontinuous phases, when
a tensile force has been acted on the outer-peripheral surface side of
the conductive belt. Then, they have presumed that, such micro-crevices
come to weaken physical binding between the continuous phase and the
discontinuous phases. As a result of that, the conductive belt's
restoring force to its original shape has weakened, and therefore, the
permanent curl has been caused.

[0025] Accordingly, the present inventors have gone through studies so as
to prevent the micro-crevices at the interfaces between the continuous
phase and the discontinuous phases, which micro-crevices are considered
to be the cause of the permanent curl, from occurring. As the result, it
is discovered that the construction, in the thickness direction of the
conductive belt, having higher crystallinity of the inner-peripheral
surface side, to which compression force is applied, than that of the
outer-peripheral surface side, to which tensile force is applied, can
suppress the occurrence of the micro-crevices at the interfaces, and it
also contributes to the reduction of the permanent curl.

[0026] The reason why the relative relationship of the crystallinity
between the inner-peripheral surface side and outer-peripheral surface
side as stated above reduces the occurrence of permanent curl is unclear,
and they presume it as stated below.

[0027] When the cylindrical conductive belt stands stretched over a
plurality of rollers, tensile force is applied to its outer-peripheral
surface side at the part where the conductive belt comes into contact
with any roller and compression force is applied to the inner-peripheral
surface side thereof, as having been stated above. On this occasion, by
decreasing the crystallinity of the outer-peripheral surface side of the
belt relative to that of the inner-peripheral surface side of the belt,
and allowing the outer-peripheral surface side to be stretchable by the
action of the tensile force acting on the outer-peripheral surface side,
stress concentration to the interfaces between the continuous phase and
the discontinuous phases is relieved. Therefore, the occurrence of the
micro-crevices at the interfaces between the continuous phase and the
discontinuous phases is believed to be suppressed.

[0028] On the other hand, at the inner-peripheral surface side, where
compressive force is to act, the compressive force acts when the belt
comes into contact with any roller, and the belt is released from the
compressive force when the contact with the roller comes free. On this
occasion, by increasing the crystallinity of the inner-peripheral surface
side of the belt relative to that of the outer-peripheral surface side,
and making more dense construction, restoration to the original shape
after the inner-peripheral surface side of the conductive belt is
released from the compressive force can be more strengthened.

[0029] As the result, as the whole conductive belt, the shape of the place
where prolonged contact with the roller comes free can easily be restored
to the original shape, and therefore, the occurrence of the permanent
curl is considered to be suppressed

[0030] Now, the construction of the cylindrical conductive belt for
electrophotography according to the present invention is described. The
conductive belt 100 according to the present invention has, at its cross
section in the peripheral direction and as shown in FIG. 1B, the
continuous phase 101 containing a thermoplastic polyester resin and the
discontinuous phases 103 each containing any one or both selected from a
polyether-ester amide and a polyether amide. Also, the discontinuous
phases 103 are present in such way as to extend in the peripheral
direction of the belt. Then, the conductive belt has a crystallinity that
is lower on the outer-peripheral surface side than on the
inner-peripheral surface side.

[0031] First, the discontinuous phases 103 each containing a
polyether-ester amide and/or a polyether amide are made present in such
way as to extend in the peripheral direction of the belt. This can make
relatively short the distance between the discontinuous phases present in
plurality. As the result, leak currents tend to flow across the
discontinuous phases present in plurality, so that the conductive belt
can be improved in its conductivity, as having such technical
significance.

[0032] The technical significance in that the conductive belt has a
crystallinity that is relatively lower on the outer-peripheral surface
side than on the inner-peripheral surface side is as stated above.
Specific crystallinity on the outer-peripheral surface side and on the
inner-peripheral surface side each may appropriately be controlled in
accordance with the diameters of rollers over which the conductive belt
is to be stretched, and its tension. A specific method of controlling the
crystallinity is detailed later as a method for producing the conductive
belt according to the present invention.

[0033] Materials for the conductive belt according to the present
invention are described next.

[0034] Thermoplastic Polyester Resin:

[0035] The thermoplastic polyester resin (hereinafter simply "PE") that
constitutes the continuous phase 101 may be obtained by polycondensation
of a dicarboxylic acid component with a dihydroxyl component,
polycondensation of a hydroxycarboxylic acid component or a lactone
component, or polycondensation making use of any of these components in
plurality. The PE may be a homo-polyester or may also be a co-polyester.

[0040] Derivatives of the above dicarboxylic acids may also be used.
Stated specifically, they may be exemplified by derivatives capable of
forming esters, e.g., lower alkyl esters such as dimethyl ester, acid
anhydrides, and acid halides such as acid chloride. Any of these
dicarboxylic acid components may be used alone or in combination of two
or more types. Preferred dicarboxylic acid components are the aromatic
dicarboxylic acids, from the viewpoint of crystallizability and heat
resistance, and much preferred are terephthalic acid, isophthalic acid
and naphthalene dicarboxylic acid.

[0047] These dihydroxyl components may be derivatives capable of forming
esters, as exemplified by alkyl group, alkoxyl group or halogen
substituted products. Any of these dihydroxyl components may be used
alone or in combination of two or more types. Of these dihydroxyl
components, it is preferable from the viewpoint of crystallizability,
heat resistance and so forth to use alkylene diols (in particular,
alkylene diols having 2 to 4 carbon atoms) and alicyclic diols.

[0048] The hydroxycarboxylic acid component may be exemplified by
hydroxycarboxylic acids such as hydroxybenzoic acid, hydroxynaphthoic
acid, diphenylene hydroxybenzoic acid and 2-hydroxypropionic acid, and
derivatives of these hydroxybenzoic acids. Any of these hydroxybenzoic
acids may be used alone or in combination of two or more types.

[0049] The lactone component may include C3 to C12 lactones such as
propiolactone, butyrolactone, valerolactone and caprolactone (e.g.,
ε-caprolactone). Any of these lactones may also be used alone or
in combination of two or more types.

[0050] Further, a polyfunctional monomer may also be used in combination
as long as the crystallizability and heat resistance are maintained. The
polyfunctional monomer may include as examples thereof polybasic
carboxylic acids such as trimellitic acid, trimesic acid and pyromellitic
acid, and polyhydric alcohols such as glycerol, trimethylol propane,
trimethylol ethane and pentaerythritol. A polyester may also be used
which has a branched or cross-linked structure, formed by the use of such
a polyfunctional monomer.

[0051] The PE may be produced by polycondensation making use of the above
component (the dicarboxylic acid component, the dihydroxyl component, the
hydroxycarboxylic acid component or the lactone component, or a plurality
of any of these components). Then, from the viewpoint of
crystallizability, heat resistance and so forth, the PE is at least one
selected from a polyalkylene terephthalate, a polyalkylene naphthalate
and a copolymer of a polyalkylene terephthalate and a polyalkylene
isophthalate. The copolymer may include, e.g., a block copolymer and a
random copolymer. The alkylene in the polyalkylene terephthalate,
polyalkylene naphthalate and polyalkylene isophthalate each may
preferably have 2 or more to 16 or less carbon atoms from the viewpoint
of crystallizability and heat resistance. The PE may further preferably
be at least one selected from polyethylene terephthalate, a copolymer of
polyethylene terephthalate and polyethylene isophthalate, and
polyethylene naphthalate. It may also be a blend or alloy of two or more
types as long as it is the thermoplastic polyester resin.

[0052] The polyethylene naphthalate may include as specific examples
thereof TN-8050SC (trade name; available from Teijin Chemicals Ltd.) and
TN-8065S (trade name; available from Teijin Chemicals Ltd.), which are
commercially available. The polyethylene terephthalate may include
TR-8550 (trade name; available from Teijin Chemicals Ltd.), which is
commercially available, and the copolymer of polyethylene terephthalate
and polyethylene isophthalate may include PIFG30 (trade name; available
from Bell Polyester Products, Inc.), which is commercially available.

[0053] The PE may preferably have an intrinsic viscosity of 1.4 dl/g or
less, much preferably from 0.3 dl/g or more to 1.2 dl/g or less, and
further preferably from 0.4 dl/g or more to 1.1 dl/g or less. As long as
it has an intrinsic viscosity of 1.4 dl/g or less, its fluidity can be
kept from lowering at the time of molding. As long as it has an intrinsic
viscosity of 0.3 dl/g or more, the conductive belt according to the
present invention can be much more improved in its strength and
durability. Here, the intrinsic viscosity of the PE is the value found by
measurement made using o-chlorophenol as a diluting solvent for the
thermoplastic polyester resin and setting the concentration of the
resultant o-chlorophenol solution to 0.5% by mass and its temperature at
2° C.

[0054] The PE may preferably be in an amount of 50% by mass or more,
particularly preferably 60% by mass or more, and further preferably 70%
by mass or more, based on the total mass of the PE and the
polyether-ester amide (PEEA) and polyether amide (PEA) detailed later. As
long as it is in an amount of 50% by mass or more, the belt for
electrophotography can more effectively be kept from lowering in
durability.

[0055] Polyether-Ester Amide (PEEA) & Polyether Amide (PEA):

[0056] The PEEA may include, e.g., compounds composed chiefly of a
copolymer consisting of a polyamide block unit such as nylon 6, nylon 66,
nylon 11 or nylon 12 and a polyether ester unit. For example, it may
include a copolymer derived from a) a lactam (e.g., caprolactam or lauryl
lactam) or a salt of aminocarboxylic acid, b) polyethylene glycol and c)
a dicarboxylic acid. The dicarboxylic acid may include as specific
examples thereof terephthalic acid, isophthalic acid, adipic acid,
azelaic acid, sebacic acid, undecane diacid and dodecane diacid.

[0057] The PEEA may be produced by a known polymerization process such as
melt polymerization. Of course, it is by no means limited to the above,
and it may also be a blend or alloy of two or more types. Commercially
available PEEAs may also be used (trade name: IRGASTAT P20; available
from Ciba Specialty Chemicals), (trade name: TPAE H151; available from
Fuji Kasei Co., Ltd.) and (trade name: PELLESTAT NC6321; available from
Sanyo Chemical Industries, Ltd.).

[0058] The PEA may include, e.g., compounds composed chiefly of a
copolymer consisting of a polyamide block unit such as nylon 6, nylon 66,
nylon 11 or nylon 12, a polyether diamine unit and a dicarboxylic acid
unit. The PEA may include as a specific example thereof a copolymer
derived from a) a lactam (e.g., caprolactam or lauryl lactam) or a salt
of aminocarboxylic acid, b) polytetramethylene diamine and c) a
dicarboxylic acid. As the dicarboxylic acid, the same as the above may be
used.

[0059] The PEA may be produced by a known polymerization process such as
melt polymerization. Of course, it is by no means limited to the above,
and it may also be a blend of two or more types of the polyether amide,
or an alloy of these. Commercially available PEA may also be used (trade
name: PEBAX 5533; available from ARKEMA Co.).

[0060] Amount

[0061] The PEEA and PEA may preferably be in a total amount of from 3% by
mass or more to 30% by mass or less, and particularly preferably from 5%
by mass or more to 20% by mass or less, based on the total mass of the
PE, PEEA and PEA. The PEEA and PEA function as conducting agents.
Accordingly, inasmuch as they are in a total amount of 3% by mass or
more, a thermoplastic resin composition used for producing the belt of
the present invention and furthermore the belt for electrophotography
produced can be made to have an appropriately low electrical resistance.
Also, inasmuch as they are in a total amount of 30% by mass or less, the
thermoplastic resin composition can well be kept from having a low
viscosity because of the decomposition of resins, and, as a result of
this, the belt for electrophotography formed can further be improved in
durability.

[0062] Additives:

[0063] Any one of both of the discontinuous phases and the continuous
phase may be incorporated with any other component(s), e.g., an
insulating filler, as long as the effect of the present invention is not
damaged. Specific examples of the insulating filler are given below: Zinc
oxide, barium sulfate, calcium sulfate, barium titanate, potassium
titanate, strontium titanate, titanium oxide, magnesium oxide, magnesium
hydroxide and aluminum hydroxide.

[0064] Production Method:

[0065] The conductive belt according to the present invention has three
characteristic features in make-up. The first feature is that it has the
continuous phase containing PE and the discontinuous phases each
containing any one or both selected from PEEA and PEA, the second feature
is that the discontinuous phases are present in such way as to extend in
the peripheral direction of the belt, and the third feature is that the
belt has a crystallinity that is lower on the outer-peripheral surface
side than on the inner-peripheral surface side.

[0066] Then, for the achievement of the first-feature make-up, it is
necessary to control how the thermoplastic resin composition used for
producing the conductive belt be formulated. More specifically, where the
mass ratio of the mass of the PE to the total mass of the thermoplastic
resin composition used for producing the conductive belt is represented
by A and the mass ratio of the total mass of the PEEA and PEA to the
total mass of the thermoplastic resin composition used for producing the
conductive belt is represented by B, it is necessary to be A>B. It may
much preferably be A/B>2.

[0067] For the achievement of the second-feature make-up, a method is
employed in which a test tube-shaped preform (a preform in the shape of a
test tube) composed of the thermoplastic resin composition specifically
formulated as above is made by biaxial orientation molding to produce a
belt in a seamless form. Such a method itself is known in the art as
disclosed in Japanese Patent Applications Laid-open No. 2006-76154 and
No. 2001-18284. A specific method for obtaining the conductive belt in a
seamless form by biaxial orientation molding is described below.

[0068] First, the test tube-shaped preform composed of the thermoplastic
resin composition is prepared. Next, the preform, having been heated, is
fitted to the interior of a seamless belt forming mold. Thereafter, the
test tube-shaped preform is stretched from its inside by using a
stretching rod, to orient the preform in its axial direction and also by
blowing a gas into the preform to orient the preform in its diametrical
direction to obtain a bottle-shaped molded product. Then, the
bottle-shaped molded product is cut at the middle thereof to obtain a
seamless belt.

[0069] The employment of such a biaxial orientation molding process
enables a conductive belt in a seamless form to be obtained in which the
discontinuous phases have been oriented in the peripheral direction and
extend in the peripheral direction. Here, the discontinuous phases may
have an aspect ratio of approximately from 10 to 30, and particularly
from 15 to 25, as average value. Here, the aspect ratio refers to the
proportion of the length (l) in the peripheral direction with respect to
the thickness maximum value (t) of discontinuous phases appearing on a
cross section when the cylindrical conductive belt is cut in a circle.

[0070] Finally, the third-feature make-up can be achieved by controlling
the crystal state of the preform composed of the thermoplastic resin
composition and having the shape of a test tube and controlling the
surface temperatures of the inner wall and outer wall of the preform when
the preform is biaxially oriented.

[0071] The test tube-shaped preform composed of the thermoplastic resin
composition is firstly required to have a state that is amorphous enough
to be feasible for the biaxial orientation, detailed later. Such a
preform may be obtained by controlling the mold temperature when the
thermoplastic resin composition is molded by injecting it into a
preform-shaped mold. Stated specifically, the thermoplastic resin
composition is quenched in the mold in the state the mold temperature is
set at a temperature sufficiently lower than the melting point of the
thermoplastic resin composition. For example, a thermoplastic resin
composition shown in Table 1 below has a melting point of 260° C.
Such a thermoplastic resin composition is molded by injecting it into a
mold temperature-controlled at a mold temperature of from 30° C.
to 40° C., whereby a preform can be obtained which is amorphous
enough to be feasible for the biaxial orientation.

[0072] Next, this amorphous preform is heated and stretched in the mold to
effect biaxial orientation, where the inner-wall heating temperature and
outer-wall heating temperature of the preform when the bottle-shaped
molded product is formed are controlled within the temperature range of
from not lower than the glass transition temperature of the thermoplastic
resin composition to not higher than the melting point of the same.
Stated specifically, the preform is so heated that its inner-wall surface
temperature may come to be ±5° C. of crystallization
temperature of the preform. Meanwhile, about the outer wall, the preform
is so heated that its outer-wall surface temperature may come to be not
lower than the glass transition temperature of the preform and not higher
than -10° C. of crystallization temperature of the same. The
preform composed of the thermoplastic resin composition shown in Table 1
above has a crystallization temperature of 170° C. Accordingly,
the preform may preferably be so heated that its inner-wall surface
temperature may come to be within the range of from 165° C. to
175° C. and its outer-wall surface temperature may come to be
within the range of from 100° C. to 160° C. Then, the
respective inner-wall surface temperature and outer-wall surface
temperature may be controlled within the above ranges, and this enables
control of the crystallinity on the inner-peripheral surface side and
outer-peripheral surface side each of the conductive belt.

[0073] Then, for the preform having been heated in such a state, the
stretching rod is used to orient the preform in its axial direction and
also blowing a gas into the preform to orient the preform in its
diametrical direction to obtain the bottle-shaped molded product. Here,
the temperature of the gas to be blown into the preform may preferably be
kept so controlled that the inner wall of the preform may not deviate
from the above temperature range during the step of orienting the
preform. Incidentally, as to the temperature of the mold with which the
surface of the bottle-shaped molded product obtained by the biaxial
orientation of the preform comes into contact, any effect it may have on
the crystallinity of the outer wall of the bottle-shaped molded product
is negligible.

[0074] The bottle-shaped molded product thus obtained is cut at the middle
thereof in a stated width to obtain the cylindrical conductive belt
according to the present invention.

[0075] The conductive belt for electrophotography may commonly have a
thickness of from 10 μm or more to 500 μm or less, and particularly
from 30 μm or more to 150 μm or less. The conductive belt may also
have volume resistivity controlled appropriately by controlling the
amount of the PE and PEEA or PEA depending on what the conductive belt is
used for. Stated specifically, where the conductive belt is used as an
intermediate transfer belt, it may have a specific volume resistivity of
approximately from 1×102 Ωcm or more to
1×1014 Ωcm or less.

[0076] Electrophotographic Apparatus:

[0077] The conductive belt according to the present invention is
described. FIG. 3 is a sectional view of a full-color electrophotographic
apparatus. In what is shown in FIG. 3, the cylindrical conductive belt
according to the present invention is used as an intermediate transfer
belt 5.

[0078] An electrophotographic photosensitive member 1 is a rotary
drum-type photosensitive member (hereinafter called "photosensitive
drum") used repeatedly as a first image bearing member, which is
rotatingly driven at a stated peripheral speed (process speed) in the
direction of an arrow. The photosensitive drum 1 is, in the course of its
rotation, uniformly electrostatically charged to stated polarity and
potential by means of a primary charging assembly 2. Then, it is
imagewise exposed to exposure light 3 emitted from an exposure means.
Thus, an electrostatic latent image is formed which corresponds to a
first color component image (e.g., a yellow color component image) of the
intended color image. Here, as the exposure means, it may include a
color-original image color-separating and image-forming optical system,
and a scanning exposure system operated by a laser scanner that outputs
laser beams modulated in accordance with time-sequential electrical
digital pixel signals of image information.

[0079] Next, the electrostatic latent image is developed with a
first-color, yellow toner Y, by means of a first developing assembly
(yellow color developing assembly 41). At this stage, second to fourth
developing assemblies (a magenta color developing assembly 42, a cyan
color developing assembly 43 and a black color developing assembly 44)
each stand unoperated and do not act on the photosensitive drum 1, and
the first-color yellow toner image is not affected by the second to
fourth developing assemblies.

[0080] The intermediate transfer belt 5 is rotatingly driven in the
direction of an arrow at the same peripheral speed as the photosensitive
drum 1. The yellow toner image formed and held on the photosensitive drum
1 passes through a nip zone formed between the photosensitive drum 1 and
the intermediate transfer belt 5, in the course of which it is
transferred to the peripheral surface of the intermediate transfer belt 5
(primary transfer) by the aid of an electric field formed by a primary
transfer bias applied to the intermediate transfer belt 5 through an
opposing roller 6.

[0081] The photosensitive drum 1 surface from which the first-color yellow
toner image has been transferred to the intermediate transfer belt 5 is
cleaned by a cleaning assembly 13. Subsequently, the second-color magenta
toner image, the third-color magenta toner image and the fourth-color
black toner image are sequentially likewise transferred superimposingly
onto the intermediate transfer belt 5. Thus, a synthesized full-color
toner image is formed which corresponds to the intended color image. A
secondary transfer roller 7 is provided in such a way that it is axially
supported in parallel to a drive roller 8 and stands separable from the
bottom surface of the intermediate transfer belt 5.

[0082] In the step of primary transfer of the first- to third-color toner
images from the photosensitive drum 1 to the intermediate transfer belt
5, the secondary transfer roller 7 may be separated from the intermediate
transfer belt 5.

[0083] The synthesized full-color toner image transferred onto the
intermediate transfer belt 5 is secondarily transferred to a second image
bearing member, transfer material P, in the following way: First, the
secondary transfer roller 7 is brought into contact with the intermediate
transfer belt 5 and simultaneously the transfer material P is fed at a
stated timing from a paper feed roller 11 through a transfer material
guide 10 until it reaches a contact nip formed between the intermediate
transfer belt 5 and the secondary transfer roller 7. Then, a secondary
transfer bias is applied to the secondary transfer roller 7 from a power
source 31. By the aid of this secondary transfer bias, the synthesized
full-color toner image is transferred (secondary transfer) from the
intermediate transfer belt 5 to the second image bearing member, transfer
material P. The transfer material P to which the synthesized full-color
toner image has been transferred is guided into a fixing assembly 15,
where this full-color toner image is heat-fixed.

[0084] After the synthesized full-color toner image has been transferred
to the transfer material P, an intermediate transfer belt cleaning roller
9 of a cleaning assembly is brought into contact with the intermediate
transfer belt 5, and a bias with a polarity reverse to that of the
photosensitive drum 1 is applied, whereupon electric charges with a
polarity reverse to that of the photosensitive drum 1 are imparted to
toners not transferred to the transfer material P and remaining on the
intermediate transfer belt 5 (i.e., transfer residual toners). Reference
numeral 33 denotes a power source. The transfer residual toners are
electrostatically transferred to the photosensitive drum 1 at the nip
zone between the photosensitive drum 1 and the intermediate transfer belt
5, and the vicinity thereof, thus the intermediate transfer belt 5 is
cleaned.

EXAMPLES

[0085] The present invention is specifically described below by giving
Examples and Comparative Examples, to which Examples, however, the
present invention is by no means limited. In these Examples and
Comparative Examples, seamless belts for electrophotography were produced
as those included in the conductive belt, and analyses and measurement of
physical properties as given in Examples and Comparative Examples were
made in the following way.

[0086] How to Measure and Evaluate Characteristic Values:

[0087] How to measure and evaluate characteristic values of the seamless
belts for electrophotography which were produced in Examples and
Comparative Examples are as follows:

[0088] (1) Volume Resistivity (ρV):

[0089] As measuring equipments, an ultra-high resistance meter (trade
name: R8340A; manufactured by Advantest Corporation) was used as a
resistance meter, and Sample Box for ultra-high resistance measurement
(trade name: TR42; manufactured by Advantest Corporation) as a sample
box. The main electrode was 25 mm in diameter, and the guard-ring
electrode was 41 mm in inner diameter and 49 mm in outer diameter
(according to ASTM D257-78).

[0090] A sample for measuring the volume resistivity of the seamless belt
for electrophotography was prepared in the following way. First, the
seamless belt for electrophotography was cut in a circular form of 56 mm
in diameter by means of a punching machine or a sharp knife. The circular
cut piece obtained was, on its one side, fitted with an electrode over
the whole surface by forming a Pt--Pd deposited film and, on the other
side, fitted with a main electrode of 25 mm in diameter and a guard
electrode of 38 mm in inner diameter and 50 mm in outer diameter by
forming Pt--Pd deposited films. The Pt--Pd deposited films were formed by
carrying out vacuum deposition for 2 minutes using a sputtering system
(trade name: MILD SPUTTER E1030; manufactured by Hitachi Ltd.), at an
electric current of 15 mA and at a distance of 15 mm between a target
(Pt--Pd) and the sample (the circular piece of the seamless belt for
electrophotography. The circular piece on which the vacuum deposition was
completed was used as a measuring sample.

[0091] The measurement was made in an atmosphere of temperature 23°
C. and relative humidity 52%. The measuring sample was previously kept
left in the like atmosphere for 12 hours or longer. The volume
resistivity was measured under a mode of discharge for 10 seconds, charge
for 30 seconds and measurement for 30 seconds and at an applied voltage
of 100 V. The volume resistivity was measured 10 times under this mode,
and an average value of the values of this measurement made 10 times was
taken as the volume resistivity of the seamless belt for
electrophotography.

[0092] (2) Crystallinity:

[0093] The belt for electrophotography obtained was cut in a size of 30
mm×30 mm, and the crystallinity was measured on the
inner-peripheral surface side and outer-peripheral surface side of the
belt for electrophotography by using the following instrument and under
the following conditions. [0094] Instrument: X-ray diffractometer
manufactured by Rigaku Corporation, RINT-2200 [0095] Output: 30 kV-50 mA
[0096] Target: Cu (CuKα) [0097] Optical system: First pinhole
collimator, 1.0 mm in diameter [0098] Receiving slits (slit made
lengthwise: 1°; slit made breadthwise: 1°) [0099] Condition
for measurement: Parallel beam collimation [0100] Rate of measurement:
10°/minute [0101] Goniometry range: 2θ=5˜40°
From the integral intensities of peaks at diffraction angles
2θ=5˜40° where diffraction peaks appear for both the
amorphous portion and crystalline portion of the resin, the crystallinity
(%) was calculated according to the following expression (1).

[0103] The belt for electrophotography was cut with a microtome or the
like at a thickness cross section in the peripheral direction of the
belt, and this cross section was observed on a field emission scanning
microscope (FE-SEM) XL30 (trade name; manufactured by FEI Technology
Co.). In an islands-in-sea structure (the sea component is the polyester
and the island component is the polyether amide) observed from the cross
section, the aspect ratios of portions corresponding to individual
islands within the range of 100 μm×100 μm were calculated by
binary-code processing to take an average value thereof.

[0104] (4) Height of Permanent Curl:

[0105] The conductive belt was fitted as an intermediate transfer belt to
an intermediate transfer unit of a laser beam printer LBP-5200
(manufactured by CANON INC.), having the apparatus structure as shown in
FIG. 3. The intermediate transfer belt of this laser beam printer was
stretched over a drive roller of 18 mm in diameter and a tension roller
of 15 mm in diameter at a stretch-over stress of 6 kgf. This laser beam
printer was left to stand at rest for a month in an environment of
temperature 35° C. and relative humidity 95%.

[0106] Next, the conductive belt was rotatingly driven by some level, and
then its part where it was in contact with the drive roller during the
leaving at rest was separated from the drive roller, in the state of
which it was left to stand at rest for a day in an environment of
temperature 35° C. and relative humidity 95% RH. Thereafter, the
height of a trail of contact of the drive roller at the part of the
conductive belt where the drive roller was in contact therewith during
the leaving at rest was measured with a surface profile analyzer (trade
name: SE-3500; manufactured by Kosaka Laboratory Ltd.). This height was
defined as permanent curl height. The larger this height is, the more any
faulty primary transfer of toner images to that part tends to occur.

[0107] (5) Image Evaluation:

[0108] After the above evaluation (4), in an environment of temperature
23° C. and relative humidity 50% RH, orange solid images were
printed on 155 g/m2 A4-size gloss paper by using yellow and magenta
two colors. The images obtained were visually observed to ascertain
whether or not any lines caused by permanent curl were seen, and
evaluation was made according to the following criteria. [0109] A: Any
line is not seen. [0110] B: Lines are seen.

[0111] Materials of Thermoplastic Resin Compositions used in Examples and
Comparative Examples:

Materials of thermoplastic resin compositions used in Examples and
Comparative Examples given later are shown in Tables 2 to 4.

[0112] Using a twin-screw extruder (trade name: TEX30α, manufactured
by The Japan Steel Works, Ltd.), the above materials were
hot-melt-kneaded under formulation shown in Table 5, to prepare a
thermoplastic resin composition. Hot-melt kneading temperature was so
controlled as to be within the range of from 260° C. or more to
280° C. or less, and hot-melt kneading time was set to about 3 to
5 minutes. The thermoplastic resin composition obtained was made into
pellets, which were then dried at a temperature of 140° C. for 6
hours. Next, the pelletized thermoplastic resin composition thus dried
was put into an injection molding machine (trade name: SE180D,
manufactured by Sumitomo Heavy Industries, Ltd.). Then, cylinder preset
temperature was set at 295° C., and the pelletized thermoplastic
resin composition was molded by injecting it into a mold
temperature-controlled at a temperature of 30° C. to prepare a
preform. The preform obtained had the shape of a test tube of 20 mm in
outer diameter, 18 mm in inner diameter and 150 mm in length. Then, by
the following method, it was ascertained that this preform was one
involving an amorphous state.

[0113] How to Ascertain Amorphous Property of Preform:

[0114] A sample of 1 mm in length and 1 mm in breadth was cut out from the
preform, and this sample was measured with a differential scanning
calorimeter (DSC). The measurement was made under conditions of heating
at from 25° C. to 300° C. at a heating rate of 10°
C./minute. Where any amorphous component remains, a crystallization
exothermic peak appears which is seen at around 170° C. Then, the
exothermic calorie of the crystallization exothermic peak in this sample
was found to be 38 J/g. Meanwhile, the endothermic calorie of the melt
endothermic peak seen at around 260° C. was found to be 62 J/g.
From the fact that the exothermic calorie of the crystallization
exothermic peak was 1/2 or more of the endothermic calorie of the melt
endothermic peak, it was ascertained that the preform retained its
amorphous component sufficiently.

[0115] Next, the above preform was biaxially oriented by using a biaxial
orientation apparatus shown in FIG. 4. Before biaxial orientation, a
preform 104 was placed in a heating unit 107 having a non-contact type
heater (not shown) for heating the outer wall and inner wall of the
preform 104, and, using an outside heater and an inside heater which were
set at temperatures shown in Table 5, the outer wall and inner wall of
the preform were so heated as to have their surface temperatures shown in
Table 5. Then, the preform 104 thus heated was placed inside a blow mold
108 kept at a mold temperature of 110° C., and oriented in its
axial direction by using a stretching rod 109. At the same time, air
temperature-controlled at a temperature of 23° C. was guided into
the preform through a blow air blowing inlet 110 to orient the preform
104 in its diametrical direction. Thus, a bottle-shaped molded product
112 was obtained. Then, the bottle-shaped molded product 112 was cut at
the middle thereof to obtain a seamless conductive belt. This conductive
belt was 70 μm in thickness. Results of evaluation of this conductive
belt are shown in Table 6.

Examples 2 to 9

[0116] Seamless belt for electrophotography were obtained in the same way
as in Example 1 except that the formulation of each thermoplastic resin
composition, the outside heater temperature, the inside heater
temperature, the outer-wall surface temperature and the inner-wall
surface temperature were made or changed as shown in Table 5. Results of
evaluation of these conductive belts are shown in Table 6.

[0117] In the above, the glass transition temperature, the crystallization
temperature and the melting point are temperature at a point of
inflection (glass transition temperature) and a peak top temperature
(crystallization temperature and melting point) which were each found
using a differential scanning calorimeter (DSC) by making their
measurement at a heating rate of 10° C./minute.

[0118] Seamless conductive belts were obtained in the same way as in
Example 1 except that the formulation of each thermoplastic resin
composition, the outside heater temperature, the inside heater
temperature, the outer-wall surface temperature and the inner-wall
surface temperature were made or changed as shown in Table 7. These
conductive belts were evaluated in the same way as in Example 1. Results
of evaluation are shown in Table 8.

[0119] Cross sections in the peripheral directions of the conductive belts
according to Examples 1 to 9 and Comparative Examples 1 to 9 were
observed on a field emission scanning microscope (FE-SEM) XL30 (trade
name; manufactured by FEI Technology Co.) at magnifications of 5,000
times. As the result, the conductive belts according to Examples 1 to 9
were, compared with the conductive belts according to Comparative
Examples 1 to 9, seen to have vastly much less come to crack at the
interfaces between the continuous phase and the discontinuous phases
present in the vicinity of their outer peripheral surfaces. Also, about
the average height of permanent curl, the conductive belts according to
Examples achieved its reduction by 45 μm at the minimum, compared with
that of the conductive belts according to Comparative Examples. Such a
difference in height of permanent curl in intermediate transfer belts has
a great influence on the transfer precision of toner images during their
primary transfer in the formation of electrophotographic images, and
furthermore the grade of the electrophotographic images.

[0120] While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed exemplary embodiments. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures and functions.

[0121] This application claims the benefit of Japanese Patent Application
No. 2010-042730, filed Feb. 26, 2010, which is hereby incorporated by
reference herein in its entirety.